In fuel cell-supported transportation systems, chemical reformers are used for obtaining the required hydrogen from hydrocarbon-containing fuels.
All the substances needed by the reformer for the course of the reaction, such as air, water and fuel are ideally supplied to the reformer in the gaseous state. However, since the fuels, such as methanol or gasoline, are generally present onboard the transportation system in liquid form, shortly before they are supplied to the reformer, they have to be heated first so as to vaporize them. This requires a pre-evaporator that is in a position to make available corresponding quantities of gaseous fuel and water vapor, the waste heat from the reformer mostly being used for the vaporization.
Since the hydrogen is mostly used immediately, chemical reformers have to be in a position to adjust the production of hydrogen to the demand, without delay, e.g. at load changes or launching phases. Especially in the cold-start phase, additional measures have to be taken, since the reformer does not make available any waste heat. Conventional evaporators are not in a position to generate the corresponding quantities of gaseous reactants without delay.
It is therefore useful to enter the fuel, by using an atomizing device, in finely divided form into the reformer. The vaporization process, at sufficient heat supply, is improved by the large surface area of the finely divided fuel.
Devices for reforming fuels are described in, for example, U.S. Pat. No. 3,971,847. In this document, the fuel is metered by metering devices that are relatively distant from the reformer, via long supply lines, into a material flow that has been brought to the right temperature and dispersed in the material flow via a dosing aperture at the end of the supply line, and this flows to the location of the actual reforming process.
In the devices disclosed, it is particularly disadvantageous that the long supply lines lead to delays and inaccuracies in fuel metering, especially in the case of strong load changes or hot-start phases. If, after a stop phase, for example, while the fuel is evaporating under the temperature influence of the supply line, fuel metering is resumed, this may lead to delayed dosing of fuel into the tempered substance stream and to the reforming process because of the dead-space volume in the supply line that has first to be replenished. The same problem arises at particularly slight load. Furthermore, long supply lines act counter to compact construction, increase error susceptibility and assembly expenditure.